pyTivo/plugins/video/transcode.py

   1 import subprocess, shutil, os, re, sys, ConfigParser, time, lrucache, math
   2 import pyTivo.config as config
   3 from pyTivo.debug import debug_write, fn_attr
   4
   5 info_cache = lrucache.LRUCache(1000)
   6 videotest = os.path.join(os.path.dirname(__file__), 'videotest.mpg')
   7
   8 def ffmpeg_path():
   9     return config.get('Server', 'ffmpeg')
  10
  11 # XXX BIG HACK
  12 # subprocess is broken for me on windows so super hack
  13 def patchSubprocess():
  14     o = subprocess.Popen._make_inheritable
  15
  16     def _make_inheritable(self, handle):
  17         if not handle: return subprocess.GetCurrentProcess()
  18         return o(self, handle)
  19
  20     subprocess.Popen._make_inheritable = _make_inheritable
  21 mswindows = (sys.platform == "win32")
  22 if mswindows:
  23     patchSubprocess()
  24
  25 def output_video(inFile, outFile, tsn=''):
  26     if tivo_compatable(inFile, tsn):
  27         debug_write(__name__, fn_attr(), [inFile, ' is tivo compatible'])
  28         f = file(inFile, 'rb')
  29         shutil.copyfileobj(f, outFile)
  30         f.close()
  31     else:
  32         debug_write(__name__, fn_attr(), [inFile, ' is not tivo compatible'])
  33         transcode(inFile, outFile, tsn)
  34
  35 def transcode(inFile, outFile, tsn=''):
  36
  37     settings = {}
  38     settings['video_codec'] = select_videocodec(tsn)
  39     settings['video_br'] = select_videobr(tsn)
  40     settings['video_fps'] = select_videofps(tsn)
  41     settings['max_video_br'] = select_maxvideobr()
  42     settings['buff_size'] = select_buffsize()
  43     settings['aspect_ratio'] = ' '.join(select_aspect(inFile, tsn))
  44     settings['audio_br'] = select_audiobr(tsn)
  45     settings['audio_fr'] = select_audiofr(inFile, tsn)
  46     settings['audio_ch'] = select_audioch(tsn)
  47     settings['audio_codec'] = select_audiocodec(inFile, tsn)
  48     settings['ffmpeg_pram'] = select_ffmpegprams(tsn)
  49     settings['format'] = select_format(tsn)
  50
  51     cmd_string = config.getFFmpegTemplate(tsn) % settings
  52
  53     cmd = [ffmpeg_path(), '-i', inFile] + cmd_string.split()
  54     print 'transcoding to tivo model '+tsn[:3]+' using ffmpeg command:'
  55     print ' '.join(cmd)
  56     debug_write(__name__, fn_attr(), ['ffmpeg command is ', ' '.join(cmd)])
  57     ffmpeg = subprocess.Popen(cmd, stdout=subprocess.PIPE)
  58     try:
  59         shutil.copyfileobj(ffmpeg.stdout, outFile)
  60     except:
  61         kill(ffmpeg.pid)
  62
  63 def select_audiocodec(inFile, tsn = ''):
  64     # Default, compatible with all TiVo's
  65     codec = 'ac3'
  66     if config.getAudioCodec(tsn) == None:
  67         type, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar =  video_info(inFile)
  68         if acodec in ('ac3', 'liba52', 'mp2'):
  69             if akbps == None:
  70                 cmd_string = '-y -vcodec mpeg2video -r 29.97 -b 1000k -acodec copy -t 00:00:01 -f vob -'
  71                 if video_check(inFile, cmd_string):
  72                     type, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar =  video_info(videotest)
  73             if not akbps == None and int(akbps) <= config.getMaxAudioBR(tsn):
  74                 # compatible codec and bitrate, do not reencode audio
  75                 codec = 'copy'
  76     else:
  77         codec = config.getAudioCodec(tsn)
  78     return '-acodec '+codec
  79
  80 def select_audiofr(inFile, tsn):
  81     freq = '48000'  #default
  82     type, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar =  video_info(inFile)
  83     if not afreq == None and afreq in ('44100', '48000'):
  84         # compatible frequency
  85         freq = afreq
  86     if config.getAudioFR(tsn) != None:
  87         freq = config.getAudioFR(tsn)
  88     return '-ar '+freq
  89
  90 def select_audioch(tsn):
  91     if config.getAudioCH(tsn) != None:
  92         return '-ac '+config.getAudioCH(tsn)
  93     return ''
  94
  95 def select_videofps(tsn):
  96     vfps = '-r 29.97'  #default
  97     if config.isHDtivo(tsn):
  98         vfps = ' '
  99     if config.getVideoFPS(tsn) != None:
 100         vfps = '-r '+config.getVideoFPS(tsn)
 101     return vfps
 102
 103 def select_videocodec(tsn):
 104     vcodec = 'mpeg2video'  #default
 105     if config.getVideoCodec(tsn) != None:
 106         vcodec = config.getVideoCodec(tsn)
 107     return '-vcodec '+vcodec
 108
 109 def select_videobr(tsn):
 110     return '-b '+config.getVideoBR(tsn)
 111
 112 def select_audiobr(tsn):
 113     return '-ab '+config.getAudioBR(tsn)
 114
 115 def select_maxvideobr():
 116     return '-maxrate '+config.getMaxVideoBR()
 117
 118 def select_buffsize():
 119     return '-bufsize '+config.getBuffSize()
 120
 121 def select_ffmpegprams(tsn):
 122     if config.getFFmpegPrams(tsn) != None:
 123         return config.getFFmpegPrams(tsn)
 124     return ''
 125
 126 def select_format(tsn):
 127     fmt = 'vob'
 128     if config.getFormat(tsn) != None:
 129         fmt = config.getFormat(tsn)
 130     return '-f '+fmt+' -'
 131
 132 def select_aspect(inFile, tsn = ''):
 133     TIVO_WIDTH = config.getTivoWidth(tsn)
 134     TIVO_HEIGHT = config.getTivoHeight(tsn)
 135
 136     type, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar =  video_info(inFile)
 137
 138     debug_write(__name__, fn_attr(), ['tsn:', tsn])
 139
 140     aspect169 = config.get169Setting(tsn)
 141
 142     debug_write(__name__, fn_attr(), ['aspect169:', aspect169])
 143
 144     optres = config.getOptres(tsn)
 145
 146     debug_write(__name__, fn_attr(), ['optres:', optres])
 147
 148     if optres:
 149         optHeight = config.nearestTivoHeight(height)
 150         optWidth = config.nearestTivoWidth(width)
 151         if optHeight < TIVO_HEIGHT:
 152             TIVO_HEIGHT = optHeight
 153         if optWidth < TIVO_WIDTH:
 154             TIVO_WIDTH = optWidth
 155
 156     d = gcd(height,width)
 157     ratio = (width*100)/height
 158     rheight, rwidth = height/d, width/d
 159
 160     debug_write(__name__, fn_attr(), ['File=', inFile, ' Type=', type, ' width=', width, ' height=', height, ' fps=', fps, ' millisecs=', millisecs, ' ratio=', ratio, ' rheight=', rheight, ' rwidth=', rwidth, ' TIVO_HEIGHT=', TIVO_HEIGHT, 'TIVO_WIDTH=', TIVO_WIDTH])
 161
 162     multiplier16by9 = (16.0 * TIVO_HEIGHT) / (9.0 * TIVO_WIDTH)
 163     multiplier4by3  =  (4.0 * TIVO_HEIGHT) / (3.0 * TIVO_WIDTH)
 164
 165     if config.isHDtivo(tsn) and not optres:
 166         if config.getPixelAR(0):
 167             if vpar == None:
 168                 npar = config.getPixelAR(1)
 169             else:
 170                 npar = vpar
 171             # adjust for pixel aspect ratio, if set, because TiVo expects square pixels
 172             if npar<1.0:
 173                 return ['-s', str(width) + 'x' + str(int(math.ceil(height/npar)))]
 174             elif npar>1.0:
 175                 # FFMPEG expects width to be a multiple of two
 176                 return ['-s', str(int(math.ceil(width*npar/2.0)*2)) + 'x' + str(height)]
 177         if height <= TIVO_HEIGHT:
 178             # pass all resolutions to S3, except heights greater than conf height
 179             return []
 180         # else, resize video.
 181     if (rwidth, rheight) in [(4, 3), (10, 11), (15, 11), (59, 54), (59, 72), (59, 36), (59, 54)]:
 182         debug_write(__name__, fn_attr(), ['File is within 4:3 list.'])
 183         return ['-aspect', '4:3', '-s', str(TIVO_WIDTH) + 'x' + str(TIVO_HEIGHT)]
 184     elif ((rwidth, rheight) in [(16, 9), (20, 11), (40, 33), (118, 81), (59, 27)]) and aspect169:
 185         debug_write(__name__, fn_attr(), ['File is within 16:9 list and 16:9 allowed.'])
 186         return ['-aspect', '16:9', '-s', str(TIVO_WIDTH) + 'x' + str(TIVO_HEIGHT)]
 187     else:
 188         settings = []
 189         #If video is wider than 4:3 add top and bottom padding
 190         if (ratio > 133): #Might be 16:9 file, or just need padding on top and bottom
 191             if aspect169 and (ratio > 135): #If file would fall in 4:3 assume it is supposed to be 4:3
 192                 if (ratio > 177):#too short needs padding top and bottom
 193                     endHeight = int(((TIVO_WIDTH*height)/width) * multiplier16by9)
 194                     settings.append('-aspect')
 195                     settings.append('16:9')
 196                     if endHeight % 2:
 197                         endHeight -= 1
 198                     if endHeight < TIVO_HEIGHT * 0.99:
 199                         settings.append('-s')
 200                         settings.append(str(TIVO_WIDTH) + 'x' + str(endHeight))
 201
 202                         topPadding = ((TIVO_HEIGHT - endHeight)/2)
 203                         if topPadding % 2:
 204                             topPadding -= 1
 205
 206                         settings.append('-padtop')
 207                         settings.append(str(topPadding))
 208                         bottomPadding = (TIVO_HEIGHT - endHeight) - topPadding
 209                         settings.append('-padbottom')
 210                         settings.append(str(bottomPadding))
 211                     else:   #if only very small amount of padding needed, then just stretch it
 212                         settings.append('-s')
 213                         settings.append(str(TIVO_WIDTH) + 'x' + str(TIVO_HEIGHT))
 214                     debug_write(__name__, fn_attr(), ['16:9 aspect allowed, file is wider than 16:9 padding top and bottom', ' '.join(settings)])
 215                 else: #too skinny needs padding on left and right.
 216                     endWidth = int((TIVO_HEIGHT*width)/(height*multiplier16by9))
 217                     settings.append('-aspect')
 218                     settings.append('16:9')
 219                     if endWidth % 2:
 220                         endWidth -= 1
 221                     if endWidth < (TIVO_WIDTH-10):
 222                         settings.append('-s')
 223                         settings.append(str(endWidth) + 'x' + str(TIVO_HEIGHT))
 224
 225                         leftPadding = ((TIVO_WIDTH - endWidth)/2)
 226                         if leftPadding % 2:
 227                             leftPadding -= 1
 228
 229                         settings.append('-padleft')
 230                         settings.append(str(leftPadding))
 231                         rightPadding = (TIVO_WIDTH - endWidth) - leftPadding
 232                         settings.append('-padright')
 233                         settings.append(str(rightPadding))
 234                     else: #if only very small amount of padding needed, then just stretch it
 235                         settings.append('-s')
 236                         settings.append(str(TIVO_WIDTH) + 'x' + str(TIVO_HEIGHT))
 237                     debug_write(__name__, fn_attr(), ['16:9 aspect allowed, file is narrower than 16:9 padding left and right\n', ' '.join(settings)])
 238             else: #this is a 4:3 file or 16:9 output not allowed
 239                 settings.append('-aspect')
 240                 settings.append('4:3')
 241                 endHeight = int(((TIVO_WIDTH*height)/width) * multiplier4by3)
 242                 if endHeight % 2:
 243                     endHeight -= 1
 244                 if endHeight < TIVO_HEIGHT * 0.99:
 245                     settings.append('-s')
 246                     settings.append(str(TIVO_WIDTH) + 'x' + str(endHeight))
 247
 248                     topPadding = ((TIVO_HEIGHT - endHeight)/2)
 249                     if topPadding % 2:
 250                         topPadding -= 1
 251
 252                     settings.append('-padtop')
 253                     settings.append(str(topPadding))
 254                     bottomPadding = (TIVO_HEIGHT - endHeight) - topPadding
 255                     settings.append('-padbottom')
 256                     settings.append(str(bottomPadding))
 257                 else:   #if only very small amount of padding needed, then just stretch it
 258                     settings.append('-s')
 259                     settings.append(str(TIVO_WIDTH) + 'x' + str(TIVO_HEIGHT))
 260                 debug_write(__name__, fn_attr(), ['File is wider than 4:3 padding top and bottom\n', ' '.join(settings)])
 261
 262             return settings
 263         #If video is taller than 4:3 add left and right padding, this is rare. All of these files will always be sent in
 264         #an aspect ratio of 4:3 since they are so narrow.
 265         else:
 266             endWidth = int((TIVO_HEIGHT*width)/(height*multiplier4by3))
 267             settings.append('-aspect')
 268             settings.append('4:3')
 269             if endWidth % 2:
 270                 endWidth -= 1
 271             if endWidth < (TIVO_WIDTH * 0.99):
 272                 settings.append('-s')
 273                 settings.append(str(endWidth) + 'x' + str(TIVO_HEIGHT))
 274
 275                 leftPadding = ((TIVO_WIDTH - endWidth)/2)
 276                 if leftPadding % 2:
 277                     leftPadding -= 1
 278
 279                 settings.append('-padleft')
 280                 settings.append(str(leftPadding))
 281                 rightPadding = (TIVO_WIDTH - endWidth) - leftPadding
 282                 settings.append('-padright')
 283                 settings.append(str(rightPadding))
 284             else: #if only very small amount of padding needed, then just stretch it
 285                 settings.append('-s')
 286                 settings.append(str(TIVO_WIDTH) + 'x' + str(TIVO_HEIGHT))
 287
 288             debug_write(__name__, fn_attr(), ['File is taller than 4:3 padding left and right\n', ' '.join(settings)])
 289
 290             return settings
 291
 292 def tivo_compatable(inFile, tsn = ''):
 293     supportedModes = [[720, 480], [704, 480], [544, 480], [480, 480], [352, 480]]
 294     type, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar =  video_info(inFile)
 295     #print type, width, height, fps, millisecs, kbps, akbps, acodec
 296
 297     if (inFile[-5:]).lower() == '.tivo':
 298         debug_write(__name__, fn_attr(), ['TRUE, ends with .tivo.', inFile])
 299         return True
 300
 301     if not type == 'mpeg2video':
 302         #print 'Not Tivo Codec'
 303         debug_write(__name__, fn_attr(), ['FALSE, type', type, 'not mpeg2video.', inFile])
 304         return False
 305
 306     if os.path.splitext(inFile)[-1].lower() in ('.ts', '.mpv'):
 307         debug_write(__name__, fn_attr(), ['FALSE, ext', os.path.splitext(inFile)[-1],\
 308                 'not tivo compatible.', inFile])
 309         return False
 310
 311     if acodec == 'dca':
 312         debug_write(__name__, fn_attr(), ['FALSE, acodec', acodec, ', not supported.', inFile])
 313         return False
 314
 315     if acodec != None:
 316         if not akbps or int(akbps) > config.getMaxAudioBR(tsn):
 317             debug_write(__name__, fn_attr(), ['FALSE,', akbps, 'kbps exceeds max audio bitrate.', inFile])
 318             return False
 319
 320     if kbps != None:
 321         abit = max('0', akbps)
 322         if int(kbps)-int(abit) > config.strtod(config.getMaxVideoBR())/1000:
 323             debug_write(__name__, fn_attr(), ['FALSE,', kbps, 'kbps exceeds max video bitrate.', inFile])
 324             return False
 325     else:
 326         debug_write(__name__, fn_attr(), ['FALSE,', kbps, 'kbps not supported.', inFile])
 327         return False
 328
 329     if config.isHDtivo(tsn):
 330         if vpar != 1.0:
 331             if config.getPixelAR(0):
 332                 if vpar != None or config.getPixelAR(1) != 1.0:
 333                     debug_write(__name__, fn_attr(), ['FALSE,', vpar, 'not correct PAR,', inFile])
 334                     return False
 335         debug_write(__name__, fn_attr(), ['TRUE, HD Tivo detected, skipping remaining tests', inFile])
 336         return True
 337
 338     if not fps == '29.97':
 339         #print 'Not Tivo fps'
 340         debug_write(__name__, fn_attr(), ['FALSE,', fps, 'fps, should be 29.97.', inFile])
 341         return False
 342
 343     for mode in supportedModes:
 344         if (mode[0], mode[1]) == (width, height):
 345             #print 'Is TiVo!'
 346             debug_write(__name__, fn_attr(), ['TRUE,', width, 'x', height, 'is valid.', inFile])
 347             return True
 348     #print 'Not Tivo dimensions'
 349     debug_write(__name__, fn_attr(), ['FALSE,', width, 'x', height, 'not in supported modes.', inFile])
 350     return False
 351
 352 def video_info(inFile):
 353     mtime = os.stat(inFile).st_mtime
 354     if inFile != videotest:
 355         if inFile in info_cache and info_cache[inFile][0] == mtime:
 356             debug_write(__name__, fn_attr(), ['CACHE HIT!', inFile])
 357             return info_cache[inFile][1]
 358
 359     if (inFile[-5:]).lower() == '.tivo':
 360         info_cache[inFile] = (mtime, (True, True, True, True, True, True, True, True, True, True))
 361         debug_write(__name__, fn_attr(), ['VALID, ends in .tivo.', inFile])
 362         return True, True, True, True, True, True, True, True, True, True
 363
 364     cmd = [ffmpeg_path(), '-i', inFile ]
 365     ffmpeg = subprocess.Popen(cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
 366
 367     # wait 10 sec if ffmpeg is not back give up
 368     for i in xrange(200):
 369         time.sleep(.05)
 370         if not ffmpeg.poll() == None:
 371             break
 372
 373     if ffmpeg.poll() == None:
 374         kill(ffmpeg.pid)
 375         info_cache[inFile] = (mtime, (None, None, None, None, None, None, None, None, None, None))
 376         return None, None, None, None, None, None, None, None, None, None
 377
 378     output = ffmpeg.stderr.read()
 379     debug_write(__name__, fn_attr(), ['ffmpeg output=', output])
 380
 381     rezre = re.compile(r'.*Video: ([^,]+),.*')
 382     x = rezre.search(output)
 383     if x:
 384         codec = x.group(1)
 385     else:
 386         info_cache[inFile] = (mtime, (None, None, None, None, None, None, None, None, None, None))
 387         debug_write(__name__, fn_attr(), ['failed at video codec'])
 388         return None, None, None, None, None, None, None, None, None, None
 389
 390     rezre = re.compile(r'.*Video: .+, (\d+)x(\d+)[, ].*')
 391     x = rezre.search(output)
 392     if x:
 393         width = int(x.group(1))
 394         height = int(x.group(2))
 395     else:
 396         info_cache[inFile] = (mtime, (None, None, None, None, None, None, None, None, None, None))
 397         debug_write(__name__, fn_attr(), ['failed at width/height'])
 398         return None, None, None, None, None, None, None, None, None, None
 399
 400     rezre = re.compile(r'.*Video: .+, (.+) (?:fps|tb).*')
 401     x = rezre.search(output)
 402     if x:
 403         fps = x.group(1)
 404     else:
 405         info_cache[inFile] = (mtime, (None, None, None, None, None, None, None, None, None, None))
 406         debug_write(__name__, fn_attr(), ['failed at fps'])
 407         return None, None, None, None, None, None, None, None, None, None
 408
 409     # Allow override only if it is mpeg2 and frame rate was doubled to 59.94
 410     if (not fps == '29.97') and (codec == 'mpeg2video'):
 411         # First look for the build 7215 version
 412         rezre = re.compile(r'.*film source: 29.97.*')
 413         x = rezre.search(output.lower() )
 414         if x:
 415             debug_write(__name__, fn_attr(), ['film source: 29.97 setting fps to 29.97'])
 416             fps = '29.97'
 417         else:
 418             # for build 8047:
 419             rezre = re.compile(r'.*frame rate differs from container frame rate: 29.97.*')
 420             debug_write(__name__, fn_attr(), ['Bug in VideoReDo'])
 421             x = rezre.search(output.lower() )
 422             if x:
 423                 fps = '29.97'
 424
 425     durre = re.compile(r'.*Duration: (.{2}):(.{2}):(.{2})\.(.),')
 426     d = durre.search(output)
 427     if d:
 428         millisecs = ((int(d.group(1))*3600) + (int(d.group(2))*60) + int(d.group(3)))*1000 + (int(d.group(4))*100)
 429     else:
 430         millisecs = 0
 431
 432     #get bitrate of source for tivo compatibility test.
 433     rezre = re.compile(r'.*bitrate: (.+) (?:kb/s).*')
 434     x = rezre.search(output)
 435     if x:
 436         kbps = x.group(1)
 437     else:
 438         kbps = None
 439         debug_write(__name__, fn_attr(), ['failed at kbps'])
 440
 441     #get audio bitrate of source for tivo compatibility test.
 442     rezre = re.compile(r'.*Audio: .+, (.+) (?:kb/s).*')
 443     x = rezre.search(output)
 444     if x:
 445         akbps = x.group(1)
 446     else:
 447         akbps = None
 448         debug_write(__name__, fn_attr(), ['failed at akbps'])
 449
 450     #get audio codec of source for tivo compatibility test.
 451     rezre = re.compile(r'.*Audio: ([^,]+),.*')
 452     x = rezre.search(output)
 453     if x:
 454         acodec = x.group(1)
 455     else:
 456         acodec = None
 457         debug_write(__name__, fn_attr(), ['failed at acodec'])
 458
 459     #get audio frequency of source for tivo compatibility test.
 460     rezre = re.compile(r'.*Audio: .+, (.+) (?:Hz).*')
 461     x = rezre.search(output)
 462     if x:
 463         afreq = x.group(1)
 464     else:
 465         afreq = None
 466         debug_write(__name__, fn_attr(), ['failed at afreq'])
 467
 468     #get par.
 469     rezre = re.compile(r'.*Video: .+PAR ([0-9]+):([0-9]+) DAR [0-9:]+.*')
 470     x = rezre.search(output)
 471     if x and x.group(1)!="0" and x.group(2)!="0":
 472         vpar = float(x.group(1))/float(x.group(2))
 473     else:
 474         vpar = None
 475
 476     info_cache[inFile] = (mtime, (codec, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar))
 477     debug_write(__name__, fn_attr(), ['Codec=', codec, ' width=', width, ' height=', height, ' fps=', fps, ' millisecs=', millisecs, ' kbps=', kbps, ' akbps=', akbps, ' acodec=', acodec, ' afreq=', afreq, ' par=', vpar])
 478     return codec, width, height, fps, millisecs, kbps, akbps, acodec, afreq, vpar
 479
 480 def video_check(inFile, cmd_string):
 481     cmd = [ffmpeg_path(), '-i', inFile] + cmd_string.split()
 482     ffmpeg = subprocess.Popen(cmd, stdout=subprocess.PIPE)
 483     try:
 484         shutil.copyfileobj(ffmpeg.stdout, open(videotest, 'wb'))
 485         return True
 486     except:
 487         kill(ffmpeg.pid)
 488         return False
 489
 490 def supported_format(inFile):
 491     if video_info(inFile)[0]:
 492         return True
 493     else:
 494         debug_write(__name__, fn_attr(), ['FALSE, file not supported', inFile])
 495         return False
 496
 497 def kill(pid):
 498     debug_write(__name__, fn_attr(), ['killing pid=', str(pid)])
 499     if mswindows:
 500         win32kill(pid)
 501     else:
 502         import os, signal
 503         os.kill(pid, signal.SIGTERM)
 504
 505 def win32kill(pid):
 506         import ctypes
 507         handle = ctypes.windll.kernel32.OpenProcess(1, False, pid)
 508         ctypes.windll.kernel32.TerminateProcess(handle, -1)
 509         ctypes.windll.kernel32.CloseHandle(handle)
 510
 511 def gcd(a,b):
 512     while b:
 513         a, b = b, a % b
 514     return a
 515